Those of ordinary skill in the art of designing and manufacturing optical devices for application in optical fiber signal transmissions are encountered with a common technical limitation that most of the passive optical devices are built by applying a thermal process with an elevated temperature that often causes a degradation of optical performance at room temperature. Techniques of thermal process (soldering, laser welding and heat-curing epoxy) are applied where the optical device is aligned, optimized, cured and packaged under an elevated temperature of more than 100° C. Furthermore, the optical devices manufactured by thermal process usually have a non-symmetric optical performance, loose distribution and poor thermal stability.
The performance and reliability of the optical devices depend heavily on their design and packaging technologies. Currently, two major kinds of design and packaging technologies, e.g., soldering based and laser-welding based technologies, are widely employed in manufacturing the passive optical devices and each of these technologies has advantages and disadvantages. The laser-welding based technology generally involves more complicated, time consuming processes and expensive equipments thus increases the production costs and limits the manufacturability. The soldering based technology is more flexible and low cost, but it is highly operator skill dependent. Device made by soldering process has poor optical performance and bad thermal stability. Furthermore, soldering and laser-welding process are usually heated up to a higher temperature at certain soldering/welding points and may adversely affect the alignment and device performance due to heat-adjustment/laser hammering process. Recently a heat-curing epoxy based technology for designing and packaging the WDM couplers is emerging, the optical components are bonded together by heat-curing epoxy. The optical devices bonded together with heat-curing epoxy usually present potential performance and reliability risk due to heat-curing process for alignment, optimization and packaging, which leads a degradation and uniformity of optical performance at room temperature.
Conventional techniques of manufacturing optical devices are further limited by other difficulties in that when several subassemblies are assembled into one device, the relative dihedral angle between optical surfaces of subassembly is random and difficult to control. The difficulties arise from the fact the assembling process involves linear alignment and angular adjustments of each subassembly in order to optimize the optical performance of device. When there are multiple parameters for adjustments and some of these parameters are functionally mutual-dependent, the processes of alignment and performance optimization become too complicate and comprises must be made to sacrifice one or several functional performance characteristics in order to manufacture the optical device within limited period of time and under a certain amount of production cost. The difficulties of performance optimization during the final assembling process are further compounded by the problems caused by the thermal effect that often takes place after the optimization process is completed and thus the efforts spent in fine-tuning the optical device are again distorted and altered when a high temperature is applied for bonding together several subassemblies by either soldering, laser-welding or heat-curing epoxy.
Therefore, a need still exists in the art of design and manufacturing of the optical devices to provide new material compositions, device structure, and manufacturing processes to overcome the difficulties discussed above. Specifically, a technique to provide the optical devices manufactured with improved structural configuration without subject the optical devices to thermal effect is required. It is further desirable that a common structural configuration and process can be applied as standard platform wherein standard process and configuration can be adapted for manufacturing a wide variety of optical devices such that the processes can be simplified and the production costs can be reduced.